The first engine swap that went into this Pro-Touring 1966 Chevelle was a 454 big block. It had some torque but it was heavy and didn’t help the handling very much. So the next engine was a lighter and more powerful 6.2L L92 out of a low milage 2008 Cadillac. The engine was upgraded with a LS3 intake system as well as a pair of Hooker headers. The transmission is a Viper T-56 with LS front plate and input shaft so it would work with the GM engine. You can check out the detailed build thread when it was still running the 454 or the photo gallery.
Source: LS1Tech